This paper presents an optimized method of gait planning for a small biped humanoid robot developed independently. The three-dimensional inverted pendulum model is adopted to gain the information of the center of gravity (COG) trajectory and angle of each robotic joint to meet the ZMP stability, transform the information into angle and speed of steering, and then realize the stable walking of the robot. The dynamic biped walking experiment based on walking parameters was taken to verify the feasibility and validity of the gait planning method.